Word Problem Regarding Time and Distance

Date: 05/30/2002 at 00:30:27
From: Dom LaRue
Subject: Word problem regarding time and distance
This is our problem of the week and I am stumped as to how to figure
out the answer. Here is the question:
A train is going through a tunnel that is 650 feet long. The train is
traveling 100 feet per second. The train enters the tunnel on one
end. Twenty-six seconds later the last car exits the other end of the
tunnel. How long is the train?
I know that I took 100 feet per second and multiplied it times 26
seconds which is 2600 feet which equals the distance of when the train
entered the tunnel and the last car exits the tunnel. I do not know
what to do with the tunnel length, whether to add or subtract. Also
is there a way to write or describe it algebraically?
Thank you for all your help.

Date: 05/30/2002 at 09:56:30
From: Doctor Ian
Subject: Re: Word problem regarding time and distance
Hi Dom,
Here is the situation just before the train enters the tunnel,
+---------------------+
[][][][][][][>| |
+---------------------+
|-------------| 650 ft
L
where L represents the length of the train. Here is the
situation just after the last car exits the tunnel:
+---------------------+
| |[][][][][][][>
+---------------------+
650 ft |--------------|
L
If '[>' is the front of the train, then in 26 seconds it moves
(650+L) feet, right? So
distance = rate * time
(650 + L) ft = (100 ft/sec) * (26 sec)
Can you take it from here?
- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/

Date: 05/31/2002 at 10:01:24
From: Dom LaRue
Subject: Thank you (Word problem regarding time and distance)
Thank you so much for the prompt reply! It really helped
me fully answer the problem for math!